ACRS Humanes 2013

Transcript

1. Effects of turbidity and sedimentation on the
   survival of Pocillopora damicornis recruits
   Adriana Humanes, Katharina Fabricius, Bette Willis, Andrew Negri
   

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2. Introduction
   Buddemeier et al. 2004, Hutchings & Haynes 2005, Hutchings et al.2005, Hoegh-Gulberg et al. 2007
   Stressors on coral reefs
   

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3. Runoff and coral reefs:
   Introduction
   Sediments and nutrient input in the Great
   Barrier Reef Lagoon have increased since 1823:
   Sediment - x 5.5
   Nitrogen- x 5.7
   Phosphorus - x 8.9
   Kroon et al. 2012
   Mitchell et al. 1997, 2001, Tilman et al. 2001, Smith et al. 2003, Devlin & Brodie 2005, Fabricius 2011
   

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4. Sediments and early life histories of corals
   Fine sediments will stay suspended and…
   Introduction
   Organic
   Carbon,
   Nitrogen
   Phosphorous
   

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5. Sediments and early life histories of corals
   Fine sediments will stay suspended and…
   Introduction
   Residence time of fine sediments, N and P: years to decades in
   the GBR lagoon
   All coral life history stages submitted to enriched sediments
   Kroon et al. 2012, Fabricius et al. 2013, Brodie et al. 2013
   

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6. Smothered
   Sed
   Fabricius et al. 2003
   Control Nut Sed + Nut
   Mortality (%)
   Introduction
   Coral spat survivorship under sediment stress:
   Tolerance to
   sediments
   At least 1 order of
   magnitude lower
   Fabricius 2005
   

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7. Objective
   To measure the survivorship
   of β-Pocillopora damicornis
   recruits exposed to
   1) three turbidity levels for 31
   days.
   2) sedimentation at several
   levels of organic enrichment.
   

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8. Experiment 1: Effects of suspended sediments on recruit survivorship
   Sediments collected in Orpheus
   and sieved ˂63 µm
   2 weeks
   0 mg/l
   124
   30 mg/l
   110
   100 mg/l
   111
   

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9. Water sample analysis:
   • Total suspended solids
   Data analysis:
   SDR: Anova
   SAR: Kruskal-Wallis
   Recruit’s size and # polyps: Kruskal-Wallis
   Survivorship: Kaplan-Meir
   Data
   Size:
   Maximum diameter
   # of polyps
   Survivorship rate:
   % recruits alive after 31 days
   • Sedimentation deposition rates (SDR)
   • Sediment attachment rate (SAR)
   • Nitrogen, Phosphorus and Carbon
   • Pigments
   • Bacterial community (454 sequencing)
   Experiment 1: Effects of suspended sediments on recruit survivorship
   

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10. N.S.
    Number of polyps/recruit
    p<0.05
    Recruits size (mm)
    0.9
    1
    1.1
    1.2
    1.3
    *
    Experiment 1: Effects of suspended sediments on recruit survivorship
    • Turbidity reduces energy for growth
    • Clearing sediments is energetically
    costly (mucus production: 2.5 x more expensive
    than other physiological functions; Riegl & Branch
    1995)
    • Trade-off between growth and
    maintenance
    Recruits size
    

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11. Experiment 1: Effects of suspended sediments on recruit survivorship
    p<0.05
    Differences
    after 18 days
    30 mg/l is as lethal as 100 mg/l for coral recruits of Pocillopora damicornis
    Survivorship (%)
    100
    80
    60
    40
    20
    0
    0 5 10 25 30
    Time (days)
    15 20
    

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12. 10
    larvae
    559
    recruits
    Sediments collected in
    Orpheus and sieved ˂63 µm
    Incubation: 24 h
    Sedimentation: 1h approximately
    4 enrichment levels
    Sample times:
    3, 6, 12, 24, 48 h
    5 vials
    Experiment 2: Effects of organically enriched sedimentation on recruit survivorship
    Survivorship: % recruits alive at each sample time and after 7 days of exposure
    Water sample analysis: Nitrogen, Phosphorus, Carbon, Pigments, Bacterial
    community (454 sequencing)
    Sediments
    Recruits
    125 vials
    Control 0.1 OC% 0.3 OC% 0.9 OC%
    

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13. Experiment 2: Effects of organically enriched sedimentation on recruit survivorship
    Time x enrichment interaction not significant
    p<0.05 p<0.05
    Enriched sediments can damage recruits of P. damicornis in less than 2 days
    Survivorship
    Exposure time (hours) Enrichment (OC%)
    

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14. Experiment 2: Effects of organically enriched sedimentation on recruit survivorship
    Enriched sediments have long-term impacts on recruits of P. damicornis
    even when removed after a couple of hours
    Survivorship 7 days after exposure
    p<0.05
    Exposure time (hours)
    

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15. Conclusions
    ü Survivorship of coral recruits and ultimately their abundance and
    distribution are negatively impacted by:
    - suspended sediments
    - organically enriched sediments
    ü Benthic habitats exposed to excessive turbidity due to river run-
    off may be sub-optimal for corals.
    

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16. Questions and
    suggestions are appreciated
    Thanks!
    

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